TPO and thyroid gland carcinoma: These abnormalities are related to a strongly reduced expression of the Natrium/Iodide Symporter (NIS) and of thyroid peroxidase (TPO) mRNA, but Tg, SLC26A4 (which encodes pendrin), Dual oxidase (Duox) and thyroid stimulating hormone receptor (TSH-R) gene expression is still present in most differentiated thyroid cancers [6,19].